Method and apparatus for forming nano-particles

ABSTRACT

Nano-scale particles of materials can be produced by vaporizing the material and allowing the material to flow in a non-violently turbulent manner into thermal communication with a cooling fluid, thereby forming small particles of the material that can be in the nano-scale size range.

PRIORITY INFORMATION

This application is a continuation application of U.S. application Ser.No. 11/687,496, filed Mar. 16, 2007, now pending, which is acontinuation of U.S. application Ser. No. 10/840,409, filed May 6, 2004,now patented as U.S. Pat. No. 7,282,167, issued Oct. 16, 2007, whichclaims priority to U.S. Provisional Application No. 60/529,724, filedDec. 15, 2003, now expired, and U.S. Provisional Application No.60/568,457, filed May 4, 2004, now expired, the entire contents of eachof which is hereby expressly incorporated by reference.

BACKGROUND OF THE INVENTIONS

1. Field of the Inventions

The inventions disclosed herein relate to the production of nano-sizedparticles. In particular, the inventions relate to the vaporization andcondensation of material for forming nano-sized particles of thematerial.

2. Description of the Related Art

Techniques for producing nanoparticles generally fall into one of threecategories, namely: mechanical, chemical or thermal processing. Inmechanical processes, nanopowders are commonly made by crushingtechniques such as ball milling. There are several disadvantages to thisapproach. The grinding media and the mill wear away and combine with thenanomaterial, contaminating the final product. Additionally,nanoparticles produced by ball milling tend to be non-uniform in sizeand shape and have a wide distribution of particle sizes.

Chemical processes can be used to create nanomaterials through reactionsthat cause particles to precipitate out of a solution, typically byreduction of organo-metallic materials. Such methods can produce powderscontaminated by unreacted materials such as carbon. Additionally,precipitation tends to form large particles and agglomerates rather thannano-scale particles.

Thermal processes utilize vaporization and quenching phases to formnano-scale particles. Such known processes have accomplishedvaporization using techniques such as joule heating, plasma torchsynthesis, combustion flame, exploding wires, spark erosion, ioncollision, laser ablation and electron beam evaporation. Plasma torchsynthesis tends to produce particles with a wide distribution ofparticle sizes as do exploding wire and combustion flame synthesis. Ioncollision and electron beam evaporation tend to be too slow forcommercial processes. Laser ablation has the disadvantage of beingextremely expensive due to an inherent energy inefficiency.

Joule heating has been used in the past to create metal vapors that werecondensed to nanomaterials in rapidly flowing turbulent quench gases.This process produces particles with a large size distribution, useslarge quantities of gas, and is difficult to scale to commercial bulkproduction.

SUMMARY OF THE INVENTIONS

An aspect of at least one of the inventions disclosed herein includesthe realization that significant improvements in particle sizedistribution can be achieved by reducing turbulence in the flows ofvaporized material and cooling gas. For example, in a thermal-typeprocess for forming nano-scale particles, a reduction in the turbulenceof the flow of vaporized material and/or cooling gas allows thevaporized particles to be quenched in a more uniform manner, therebyresulting in better (e.g., narrower) particle size distribution.

One inventive method of producing nano-scale particles comprises thesteps of feeding a material onto a heater element so as to vaporize thematerial, allowing the material vapor to flow upwardly from the heaterelement in a laminar manner under free convection, injecting a flow ofcooling gas upwardly from a position below the heater element,preferably parallel to and into contact with the upward flow of thevaporized material and at the same velocity as the vaporized material,adjusting the flow of cooling gas so as to maintain a laminar flow ofthe vaporized material and cooling gas, allowing the cooling gas andvaporized material to rise and mix sufficiently long enough to allownano-scale particles of the material to condense out of the vapor, anddrawing the mixed flow of cooling gas and nano-scale particles with avacuum into a storage chamber.

Another inventive method of producing nano-scale particles comprises thesteps of vaporizing a material with a heater device, allowing thematerial vapor to rise under substantially free convection, andinjecting cooling gas into thermal communication with the flow ofvaporized material. Other aspects of the inventions herein compriseapparatus and structure arranged and configured to carry out theinventive methods taught herein and variations thereof. Further featuresand advantages of the present inventions will become apparent to thoseof skill in the art in view of the detailed description of preferredEmbodiments that follows, when such description is considered inconjunction with the attached figures and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a cross-sectional view of anano-scale particle generator having a vaporization system, a coolingfluid delivery system, and a collection system.

FIG. 2A is a front elevational and partial cross-sectional view of amodification of the nano-scale particle generator illustrated in FIG. 1,a chamber housing portions of the vaporization and cooling fluiddelivery systems being shown in section.

FIG. 2B is an enlarged partial sectional view of the cooling fluiddelivery system of FIG. 2.

FIG. 3 is a partial cut-away and left side elevational view of thenano-scale particle generator illustrated in FIG. 2.

FIG. 4 is an enlarged schematic side elevational view of portions of thevaporization and cooling fluid delivery systems of FIG. 2, vaporizedmaterial and cooling fluid flows being represented by arrows.

FIG. 5 is a schematic top plan view of a heating element of thevaporization system illustrated in FIG. 4, vaporized material andcooling fluid flows being represented by arrows.

FIG. 6 is an enlarged schematic illustration of a portion of thecollection system of FIG. 2, the flow and separation of solidifiednano-particles and cooling fluid being represented by arrows, circles,and stars.

FIG. 7 is a color photograph illustrating a top plan view of a portionof a modified vaporization system in operation and a flow of vaporizedmaterial emanating from a heater element of the vaporization system, theflow of vaporized material being cooled by a cooling fluid and risingwith some turbulence.

FIG. 8 is another color photograph showing a top plan view of the heaterelement shown in FIG. 7, in operation.

FIG. 9 is a color photograph illustrating another top plan view of theheater in operation and a flow of vaporized material emanating from theheater element, the flow of vaporized material being cooled by a coolingfluid and rising without visually perceptible turbulence.

FIG. 10 is a wider angle color photograph of the heater in operationshown in FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description and examples illustrate preferred embodimentsof the present inventions in detail. Those of skill in the art willrecognize that there are numerous variations and modifications of theseinventions that are encompassed by its scope. Accordingly, thedescription of preferred embodiments should not be deemed to limit thescope of the present inventions.

“Quench gas” or “quenchant gas” as used in this specification refers toa gas that has a cooling effect on a material and may, depending uponthe ambient conditions, induce a phase change in the material. As usedwithin this specification, the term “substantially laminar” includesgenerally smooth fluid flows that may be completely laminar as well asflows that include turbulent portions, as described and illustratedbelow, and flows including incidental or transient eddies. The term“substantially free convection,” as used in this specification, includesmovement of fluids (including gases) due to energy gradients andcompletely free convection, but may also include fluid movement that isslightly influenced by a vacuum pump as described herein. The term“chamber” is intended to carry its ordinary meaning and may includewithout limitation a vessel or container completely or partiallyenclosing a space, for example, where a gas curtain or other confiningmeans form a wall of the chamber.

Apparatus For Forming Nano-Particles

With reference to FIG. 1, one embodiment of an inventive nano-particlegenerator 10 comprises a particle generation system 110 and a collectionsystem 210, which can include a vacuum system 310. The generator 10 alsopreferably comprises a controller 410. With such a nano-scale particlegenerator 10, particles can be formed by the particle generation system110, optionally utilizing the vacuum system 310 and the controller 410,and delivered for storage and recovery in the collection system 210. Inone embodiment, the particle generation system 110 comprises a firstchamber 112, a cooling fluid delivery system 510 for delivering coolingfluid, a vaporization system 610 for vaporizing a material, and amaterial feeder 710, some or all of which may be included within thefirst chamber 112. Examples of each of these subsystems are describedseparately below.

In one embodiment, the material feeder 710 is configured to feed one ofany type of vaporizable material, e.g., zinc, into the first chamber112. The material can be in any form, including by example only powder,pellet, sheet, bar, rod, wire, ingot, and the like. The material feeder710 is configured to feed the material in the form provided sufficientlyclose to the vaporization system 610 to cause the material to vaporize.Thus, in one exemplary but non-limiting embodiment, where the materialis in wire form, the material feeder 710 can be in the form of awire-feeder device.

Preferably, the material feeder 710 is configured to feed thevaporizable material at a desired rate. A further advantage is providedwhere the feed rate of the feeder 710 can be adjusted. For example,where the feeder 710 is a wire-feeder device, the feeder 710 can includea mechanism for adjusting the speed at which the wire is dischargedtherefrom.

In the first chamber 112, the vaporization system 610 is provided andconfigured to vaporize the material. The vaporization system 610 cancomprise any type of device capable of generating a reduced-turbulenceflow of vaporized material. A further advantage is achieved where thevaporization system is configured to produce a smooth, substantiallyand/or completely turbulence-free flow of vaporized material. Such avaporization system 610 can comprise, for example, but withoutlimitation, a heater device that can be operated in such a manner thatthe vaporized material can rise from the device under substantially freeconvention and/or in a substantially laminar manner.

In one exemplary embodiment, the vaporization system 610 comprises anelectrical resistance heater preferably configured to allow materialfrom the feeder 710 to vaporize and emanate from the heater in a smoothflow. For example, but without limitation, the heater and the feeder 710can be arranged such that the material from the feeder 710 is vaporizedby heat from the heater. Because the source of heat, or the outersurface of the heater, is stationary, the flow of vaporized material canflow smoothly away from the heater. Other heater devices can also beconfigured to provide such a smooth flow of vaporized material. Forexample, but without limitation, where the source of heat is notstationary, such as with a plasma gun heater device, other devices maybe used to smooth the flow of vaporized material, such as aplenum/venturi fluid flow device. The smooth flow of vaporized materialcan thermally communicate with a cooling fluid from the cooling fluiddelivery system 510 with reduced turbulence, and thus, enhanced particlecharacteristics.

The cooling fluid delivery system 510 is configured to provide a smoothflow of cooling or quenchant fluid (such as, for example, but withoutlimitation, one or any combination of Helium, Hydrogen, Nitrogen, Argon,and the like) that flows into thermal communication with the vaporizedmaterial emanating from the vaporization system 610. The cooling fluidsupplied from the cooling fluid delivery system 510 can thermallyinteract with the vaporized material from the vaporization system 610with reduced turbulence.

A further advantage is provided where the cooling fluid delivery system510 is configured to direct a flow of cooling fluid generally parallelto and at about the same speed as the vaporized material emanating fromthe vaporization system 610. This configuration allows the cooling fluidto thermally interact with the flow of vaporized material with reducedturbulence. For example, but without limitation, the cooling fluiddelivery system 510 can be configured to direct a flow of cooling fluidupwardly toward the flow of vaporized material emanating from thevaporization system 610, at about the same speed as a stable portion ofthe flow of vaporized material flowing upwardly from the vaporizationsystem 610. The flow of cooling fluid can flow into thermalcommunication with the flow of vaporized material without excessivelyinterfering with the smooth convective flow of the vaporized material.

In some embodiments, the controller 410 is configured to obtain feedbackfrom each of the controllable systems as well as to send controlinformation to those systems. Optionally, the controller 410 interfaceswith an operator who can input specific information and commands to thecontroller and controllable systems. The contemplatedcontroller-operator interface can comprise visual displays such asdials, gauges, digital character displays, audio signals, light-emittingdiodes, computer screens, liquid crystal displays, etc. The contemplatedcontroller-operator interface can also include manipulable input devicessuch as knobs, levers, buttons, switches, keyboards, joysticks,trackballs, mice, touch-screens, etc.

It is contemplated that the controller 410 can be a hard-wired device orone of a plurality of software-based computer routines. Such computerroutine(s) can be part of a larger control program or an independentprogram. The control program can be configured to run on a dedicatedprocessor or a general purpose processor. The controller 410 can be asingle independent unit or multiple units. Where the controller 410comprises multiple units, those units can be dependent upon orindependent of each other.

The collection system 210 is optionally configured to capture theparticles resulting from the thermally communicating flows of vaporizedmaterial and cooling fluid. In one exemplary embodiment, the collectionsystem 210 comprises a chamber connected to the vaporization system 610.Optionally, the vacuum system 310 can be used to generate a fluid flowout of the collection device. For example, but without limitation, thevacuum system 310 can be configured to draw gases from the secondchamber 212 and to discharge those gases to the exterior of the secondchamber 212. The vacuum can aid in maintaining a smooth flow ofparticles and cooling fluid from the first chamber 112. The vacuumsystem 310 can be configured to generate any magnitude of vacuum withinthe collection system 210. Advantageously, the vacuum system 310 isconfigured to generate a relatively small vacuum within the collectionsystem 210, such as, for example, but without limitation, a few Torrbelow the pressure exterior to the collection system 210.

Optionally, the vacuum generated by the vacuum system 310 can besufficiently large to affect the flow of vaporized material and coolingfluid within the first chamber 112. Preferably, while the vacuum can beused to speed up the flow of cooled particles and cooling fluid from thefirst chamber 112, the magnitude of the vacuum is limited so as toprevent disturbance of the flow of vaporized material, cooling fluid,and cooled particles flowing upwardly from the vaporization system 610.

Optionally, the collection system 210 can include a nano-particle filter(not shown). The vacuum system 310 can be configured to draw gases fromthe second chamber 212 through a nano-scale filter so as to minimize orprevent particles from being pulled through the vacuum system 310 anddischarged to the atmosphere.

During operation of the generator 10, material is fed by the materialfeeder 710 to the vaporization system 610. The vaporization system 610vaporizes the material, causing the vaporized material to flow upwardlyfrom the vaporization system 610 in a reduced-turbulence manner.Preferably, the flow of vaporized material rises from the vaporizationsystem 610 in a substantially laminar flow and/or under substantiallyfree convection and may, in at least one embodiment of generator 10,rise from the vaporization system 610 in the form of a stable plume,similar in shape to that of a candle flame. The cooling fluid isdischarged from the cooling fluid delivery system 510 into thermalcommunication with the flow of vaporized material.

Optionally, cooling fluid is discharged from the cooling fluid deliverysystem 510 into thermal communication with the flow of vaporizedmaterial. Preferably, the cooling fluid is discharged in a manner thatdoes not disrupt the smooth flow of the vaporized material.

As the vaporized material flows away from the heater, individual atomsof the vapor begin to cool and coalesce into multi-atom droplets and/orparticles. Because of the surface tension the liquid droplets formalmost perfect spheres. As these multi-atom particles or dropletsthermally communicate with the cooling fluid, the liquid dropletssolidify into solid spherical particles.

The cooling fluid flows into the collection system 210 with theparticles entrained within the fluid flow. As this flow enters thesecond chamber 212, the flow slows thereby allowing the particles tofall out of the moving flow and collect in the second chamber 212.Preferably, the vacuum system 310 is used to generate a low magnitudevacuum within the second chamber 212, so as to enhance the stabilityand/or continuity of the flow from the first chamber 112 into the secondchamber 212.

With reference to FIG. 2A, another embodiment of the nano-particlegenerator 10 is illustrated therein and is identified generally by thereference numeral 10′ (ten prime). The components of the generator 10′corresponding to the respective components of the generator 10 areidentified with the same reference numerals used with respect to thegenerator 10, except that a prime symbol “′” has been added thereto.

The generator 10′ includes a first chamber 112′ that defines anenclosure. In the illustrated embodiment, the first chamber 112′ is agenerally cylindrical metal tank oriented vertically and tapered at thetop to generally form a generally frustroconical shape.

As illustrated in FIG. 2A, the first chamber 112′ has a lower region114, and an upper region 116. In this embodiment, the lower region 114is separated from the upper region 116 by a diffuser 118. Within theupper region 116 are situated a heater device 610′ with a supportingstrut 120, and a material feeder 710′.

The general shape of one embodiment of the first chamber 112′,illustrated in FIG. 2, has a cross-section with generally parallel walls122. At an upper end of the chamber 112′, the sides slope inwardlyforming upper walls 124 until they meet a tube 150 that extends upwardlyfrom the top of the first chamber 112′. In this embodiment, the firstchamber 112′ is generally symmetric about an axis extending from thebottom of the chamber 112′ to the top of the chamber where the tube 150is situated. Optionally, the outer surfaces of the walls 122, 124 of thefirst chamber 112′ are in thermal communication with and generallycovered by two cooling jackets, a lower cooling jacket 850, and an uppercooling jacket 852. The cooling system is described below in greaterdetail.

As illustrated in FIG. 2A, certain embodiments can have a plurality ofopenings in the first chamber 112′, including the tube 150 at the top ofthe chamber. The lower end 152 of the tube 150 is connected to the upperwall 124 of the first chamber 112′ so as to connect the interior of thefirst chamber 112′ to the interior of the second chamber 212′.Preferably, the lower end 152 is connected to the upper wall 124 suchthat no air or gas can escape the first chamber 112′ or the tube 150 atthe junction.

In an exemplary but non-limiting embodiment, the first chamber 112′ canbe manufactured from sheets of metal that have been welded together inthe described shape, with any openings sealed shut by welding, gaskets,liquid sealant, or other techniques. In this exemplary embodiment, thefirst chamber 112′ has a width at the base of approximately 3.5 feet anda height of approximately 6 feet from the floor to the lower end 152 ofthe tube 150. The walls 122, 124 of the first chamber 112′ are formedfrom metal and are sealed so that gas cannot easily penetrate into thechamber 112′ from outside or escape from within the first chamber 112′.

Preferably, the first chamber 112′ includes a window 160 arranged toallow an operator of the generator 10′ to view the vaporization and/orthe quenching of vaporized material occurring in the vicinity of theheater device 610′. Optionally, the window can be configured for theinsertion or orientation of an instrument for observing the vaporizationor quenching during operation. In the illustrated embodiment, the window160 comprises a transparent panel sealed to the upper wall 124. Thedescribed configuration allows an operator to look downwardly and viewthe vaporization and/or quenching during operation. Optionally, a camera162 can be used to capture a video image or images of the vaporizationand/or quenching during operation. In the illustrated embodiment, thecamera 162 is oriented to peer downwardly toward the heater device 610′and capture images of the heater device 610′ and the vaporization andquenching of material in the vicinity of the heater device 610′.

With continued reference to FIG. 2A, the second chamber 212′ can be agenerally cylindrical metal tank, situated generally above and to theside of the first chamber 112′, with the two chambers being connected bythe tube 150. The tube 150 preferably is metal, although other suitablematerials can be used. The second chamber 212′ is supported at a heightgenerally above the first chamber 112′ by a plurality of legs 213. Thelegs 213 can be configured to support the second chamber 212′ five orsix feet above the floor, although other positions can also be used. Inthe illustrated embodiment, the second chamber 212′ can have the samegeneral shape as the first chamber 112′. FIGS. 3 and 6 provide otherviews of the second chamber 212′. It is contemplated that the secondchamber can comprise any suitable container, and can be constructed ofthe same materials as the first chamber 112′, with metal walls andrivets or other fastening devices or techniques used to hold the metalwalls together. The second chamber 212′ is generally airtight, but hasat least two openings, including one to allow the connection of the tube150 at the end of the tube 154.

Another opening in the second chamber 212′ is disposed at a longitudinalend 224 of the second chamber 212′, where a tube 330 connects to thesecond chamber 212′. The tube 330 connects to the second chamber 212′ atthe longitudinal end 224 thereof. The tube 330 connects the secondchamber 212′ to the vacuum system 310′. The tube 330 incorporates atleast one valve 332, which can be adjusted to regulate the flow of gasthrough the tube 330. The tube 330 is connected to the second chamber212′ and the vacuum system 310′ using pressure fits, including at leastone clamp 334 so that gas is not allowed to escape from the twojunctures 224, 336.

The second chamber 212′ is separated into two regions, 218 and 220A by afilter 222, shown in cross-section inside the second chamber 212′ inFIG. 2. The filter is situated generally toward the end 216 of thesecond chamber 212′. The filter 222 is configured to contact the sidesof the second chamber 212′, and is placed between the opening where thetube 150 enters the second chamber 212′ and the opening where the tube330 connects to the second chamber 212′ so that the filter 222 allowsnanoparticles to enter the second chamber 212′ but not to escape to theambient.

In the embodiment illustrated in FIG. 2A, cooling fluid delivery system510′ comprises a source of cooling gas, which, in this embodiment,comprises multiple gas tanks 520 with valves 526 connected to tubes 530which in turn connect to a mixer 540. The mixer 540 includes aprotruding pipe 550. The cooling fluid delivery system 510′ isconfigured to supply gas to be passed through the diffuser 118 andtoward the heater device 610′. The pipe 550 penetrates the wall of thefirst chamber 112′. In this embodiment, the pipe 550 extends from theoutside of the first chamber 112′ into the lower region 114 of the firstchamber 112′. The pipe 550 is configured to guide cooling gas to passfrom outside the first chamber 112′ into the lower region 114 of thefirst chamber 112′. Preferably, the pipe 550 does not allow air fromoutside the system into the first chamber 112′, and does not allow gasfrom inside the first chamber 112′ to escape therefrom. The lower region114 can serve as a “plenum.” One alternative embodiment of the diffuser118 is described below with reference to FIG. 2B.

In one embodiment, the gas tanks 520 can be commercially available metalpressurized gas tanks. The gas tanks 520 have flow regulator valves 526with knobs 528 that can be turned to decrease or increase the flow ofgas from the tank into the connected tubes 530. The tubes 530 areconnected to the mixer 540 and the tanks 520 in such a way that gas doesnot escape and no outside air can penetrate the cooling fluid deliverysystem 510′. The pipe 550 that connects the mixer 540 with the lowerregion 114 of the first chamber 112′ is connected to the mixer 540 andthe first chamber 112′ in such a way as to not allow any outside air topenetrate into the nano-particle generator 10′, but to allow gas to movefrom the mixer 540 through the wall 122 of the first chamber 112′ intothe lower region 114 of the first chamber 112′. It is contemplated thatmore permanent gas tanks may be used, as for example, for large scaleproduction.

It is contemplated that the cooling fluid delivery system 510′ could bea commercially available system or any equivalent known by those ofordinary skill in the art. The cooling gas or gases used can be any puregas or mixture of inert or reactive gases including, but not limited to,argon, helium, hydrogen, nitrogen, carbon dioxide and oxygen. Materialsthat can be vaporized at elevated temperatures and/or reduced pressurescan also be used as cooling gases.

The diffuser 118 within the first chamber 112′ can be any type ofcommercially available diffuser. Preferably, the diffuser 118 is madefrom a sintered material such as, for example, but without limitation,stainless steel. The diffuser 118 is configured to allow the cooling gasto move from the lower region 114 to the upper region 116 with agenerally uniform flow profile. The described configuration allows thecooling gas to move evenly around the heater device 610′ and flowsmoothly into thermal communication with a flow of vaporized materialemanating from the heater device 610′. A further advantage is providedwhere the diffuser 118 is larger than the heater device 610′. In such anembodiment, the diffuser 118 can provide a flow of cooling gas thatsurrounds a flow of vaporized material emanating from the heater device610′, thereby further enhancing the flow of the cooling gas into thermalcommunication with the flow of vaporized material, described in greaterdetail below.

In some embodiments, different kinds of cooling gas can be mixed priorto passing through the diffuser 118. For example, if an operator wishesto raise the heat capacity of a mixture of cooling gas, the operator canmix in a second cooling gas that has a higher heat capacity. In thisway, the cooling capacity of a desired volume of mixed cooling gases canbe raised. Optionally, the cooling gases can be mixed to the desiredproportions and stored in a single tank ready for use with the generator10′. If desired, a mixing device (not shown) can be connected to firstand second gas supplies providing first and second cooling gases. Such amixing device can be configured to mix the first and second gases andcontinuously supply the mixed gases to the lower portion 114 or thediffuser 118. Such a mixer may be of a type commercially available. Forexample, in an exemplary but non-limiting embodiment, an MKS brandmixer, such as model no. 247 can be used.

FIG. 2B illustrates an alternative embodiment of the diffuser 118 ofFIG. 2A. FIG. 2B is a cross-sectional view detailing a modification ofthe diffuser 118, identified generally with the reference numeral 119.The diffuser 119 is configured for diffusing a flow of cooling gas intothe first chamber 112′. Components of the diffuser 119 that are the sameas the diffuser 118 have been given the same reference numerals, exceptthat a letter “B” has been added.

In this embodiment, the diffuser 119 has a plenum 114B into which thepipe 550B feeds the cooling gas. The plenum 114B can be bounded by asolid metal plate 130 below, and a sintered metal plate 119 above. In anexemplary but non-limiting embodiment, the sides of the diffuser 188Bcan be comprised of a stainless steel welding rod 134, welded intoplace. The welding rod serves to hold the two plates and to seal theplenum 114B so that cooling gas can only escape through the sinteredmetal plate 119. In one embodiment, the diffuser 119 is supported bymetal legs 138.

Referring back to FIG. 2A, in a preferred embodiment, a heater device610′ is situated in the upper region 116 of the first chamber 112′ andis supported above the diffuser 118, 119. The heater device 610′comprises a heating element 612 supported by two supporting struts 120.In this embodiment, one supporting strut 120 is connected to the side ofthe first chamber 112′ and extends inwardly and the second is connectedto the flow of the chamber and extends upward. The struts hold theheating element 612 generally in the upper region 116 of the firstchamber 112′ and above the diffuser 118.

In an exemplary but non-limiting embodiment, the heating element 612 canbe approximately 200 millimeters long. The heating element 612 can beprovided with an electrical current that heats the element 612 as theelectrical current flows from one end of the element 612 to the other.In one embodiment, the heater device 610′ comprises a titanium-diborideheater bar, such as that commercially available from a company known asAdvanced Ceramics. Preferably, the heating element 612 is configured tomaintain and withstand temperatures sufficient to vaporize the desiredmaterial. In an exemplary but non limiting embodiment, the heatingelement 612 can have a surface temperature of about 500 degrees Celsiusand is configured to vaporize zinc. Additionally, the heating elementcan be of any size, thickness, shape, or length.

Generally, when the heating element 612 vaporizes a material, thevaporized material can flow upwardly in a fluidic flow. If the flow isnot meaningfully disturbed, the flow will resemble the shape of theflame of a candle. In one exemplary but non-limiting embodiment, thefirst chamber 112′ is sized so that the flow is allowed to rise abovethe heater element 612 to a height of about three-times the length ofthe heater element 612. This provides a further advantage in that therewill be sufficient time for the cooling effect of the cooling fluid,described in greater detail below, to achieve a high narrow qualityparticle size distribution.

In some contemplated embodiments, the heater device 610′ comprises acommercially available electrical resistance element heater. The heaterdevice 610′ can also be a hollow tube furnace or slot furnace. Thematerial can be any vaporizable material. Advantageously, the materialcan be any pure metal, oxide or alloy that can be evaporated by theheating source, usually at a low pressure, in the particle generator10′.

Referring to FIG. 2A, in some embodiments, the material feeder 710′ cancomprise an access tube 730, with an inner end 732 and an outer end 734.Additionally, the material feeder 710′ can further comprise a materialfeeder device 720 supported by a support member 722 that connects thewall 122 of the first chamber 112′ with the material feeder device 720.Preferably, the access tube 730 is configured to allow material 910 toenter the first chamber 112′ through the wall 122 of the first chamber112′ without allowing air from outside the first chamber 112′ topenetrate the interior of the first chamber 112′. As shown in FIG. 2,the material feeder 710, is positioned higher than the heating element612 with the inner end 732 of the access tube 730 directly above theheating element 612 such that the material 910, when melted, dripsdirectly onto the heating element 612. The material 910 may comprisemetal wire. It is contemplated that the material feeder 710′ cancomprise any system, commercially available or otherwise, but that inone embodiment the material feeder 710′ is configured to feed a thinmetal wire through the wall of the first chamber 112′ at an adjustablerate.

In another embodiment, the material feeder 710′ and the heating element612 can be combined in function so that the material is melted and flowsinto the first chamber 112′ in a liquid form. It is contemplated thatthe material can be in any of a number of forms instead of wire, such asingots or pellets. The material can be any pure metal, oxide or alloythat can be evaporated by the heating element 610.

In the embodiment illustrated in FIG. 2, the vacuum system 310′ is acommercially available unit that is connected to the collection system210′ by a tube 330. The vacuum system 310′ is located at a distance fromthe first chamber 112′ and the second chamber 212′, in part to minimizeunwanted vibrations from transferring between the vacuum system 310′ andthe first chamber 112′. In this embodiment, the vacuum system produces amild vacuum gently urging the gas within the first chamber 112′ and thesecond chamber 212′ to flow upwardly through the diffuser 118 past theheating element 612 through the tube 150 into the second chamber 212′from the first region 218 of the second chamber 212′ through the filter222 into the frustroconical region 220 of the second chamber 212′through the valve 332 and tube 330 and into the vacuum system 310′. Inthe current embodiment, the vacuum system 310′ is connected to anelectrical power grid through an electrical plug. In one embodiment, thevacuum system 310′ can be insulated to minimize excessive sound andvibration.

It is contemplated that the vacuum system 310′ can comprise any suitablevacuum system, commercially available or otherwise. In one embodiment,the vacuum system 310′ is connected to the second chamber 212′ by a tubeso that the vacuum system slightly reduces the pressure inside thevolume of space inside the first chamber 112′, the second chamber 212′and the tube connecting the two chambers. Preferably, during operation,the vacuum system 310′ draws a volumetric flow rate that is generallyequal to the volumetric flow rate of the cooling gas from the diffuser118. In one exemplary but non-limiting embodiment, the vacuum system310′ can comprise a Leybold-Heraeus D60 roughing pump and RUVAC blower.

In the embodiment illustrated in FIG. 2, a cooling system 810 comprisesa coolant tank 820, a pump 840, a valve 822, a tube 830, and two coolingjackets 850 and 852. In this embodiment, a coolant, such as for example,but without limitation, water, is circulated from the water tank 820 bythe pump 840 through the tube 830 and the valve 822 into the coolingjackets 850 and 852 and back into the coolant tank 820 through the tube830 and valve 822. The pump 840 can be connected to and obtain powerfrom an electrical power grid through a conventional electrical powersupply.

It is contemplated that the cooling system 810 can comprise any suitablecooling system, commercially available or otherwise. The cooling system810 can use water, air, sound waves, evaporation, active refrigeration,or any other known method for controlling temperature. In one exemplarybut non-limiting embodiment, the cooling system can comprise acommercially available water chiller known as a Neslab HX-300.

In the embodiment illustrated in FIG. 2, a video camera 162 ispositioned to gather optical data through the window 160 and issupported by a camera support member 164 that is connected to the outerwall 122 of the first chamber 112′. The angle of the camera 162 is suchthat the camera 162 can capture video images of the heating element 612,the vaporizing material 910, as well as the quenching of the material910. The camera 162, in this embodiment, is powered by batteries. Inthis embodiment, the camera is sensitive to visible light and has a lenswith a focal length that can be adjusted by the user. The camera 162records data on a conventional, commercially available, analog ordigital video tape. Other video capturing devices can also be used.

It is contemplated that many alternatives can fulfill the function ofthe camera 162. Feedback can be provided in real time to the operatorthrough a monitoring screen in communication with the camera 162. Acomputer can be configured to monitor the status of the first chamber112′ and provide feedback with which to adjust the various systems. Thedata can be obtained in digital or analog form. The camera can also besensitive to radiation that is not in the visible range, such asinfrared or ultraviolet radiation.

In the embodiment illustrated in FIG. 2, the controller 410′ can be asingle unit that is electrically or mechanically connected to each ofthe controllable systems of the generator 10′. The controller 410′ canbe connected to the vacuum system 310′ by a wire 412. The controller410′ can also be connected to the camera by a wire 414. The controller410′ can further be connected to the cooling system 810 and pump 840 bya wire 416. The controller 410′ can be connected to the material feeder710′ by a wire 418. The controller can be connected to the heatingelement 612 by a wire 420. The controller 410′ can be connected to thecooling fluid delivery system 510′ by a wire 422.

In some embodiments, the controller 410′ is configured to obtainfeedback from each of the controllable systems as well as send controlinformation to those systems. The controller 410′ also interfaces withan operator, who can input specific information and commands to thecontroller and controllable systems. The contemplatedcontroller-operator interface can comprise visual displays such asdials, gauges, digital character displays, audio signals, light-emittingdiodes, computer screens, liquid crystal displays, etc. The contemplatedcontroller-operator interface can also include manipulable input devicessuch as knobs, levers, buttons, switches, keyboards, joysticks,trackballs, mice, touch-screens, etc.

It is contemplated that the controller 410′ can comprise separatecontrol modules, one for each of the controllable systems of theinventions. In other embodiments, the controller can be a single unitconfigured to communicate with and control each of the controllablesystems of the generator 10′. The controllable systems of the generator10′ include, for example, but without limitation, the material feeder710, the heater device 610′, the cooling fluid delivery system 510′, thecooling system 810, and the vacuum system 310′.

The controller 410′ can comprise a computer system configured to performthe control functions. A computer control system can replace theoperator by analyzing feedback data and adjusting the adjustable systemsappropriately according to parameters determined concurrently orbeforehand.

Method of Forming Nano-Particles

A method of generating nano-particles can comprise a material feedingprocess, a material vaporization process, and a cooling process that maycomprise an introduction of a flow of cooling fluid to interact with thevaporized material. Optionally, the method can include drawing thevaporized material and cooling fluid using a vacuum system, storing, andcollecting the nanoparticles. One exemplary but non-limiting embodimentof a method of producing nanopowders generally comprises the steps ofcreating a material vapor stream in a first chamber 112′ and convertingthe vapor into nanoparticles using a plume of quenchant gas. Optionally,the method can include adjusting or controlling the speed of thematerial feeding process, adjusting or controlling the rate of materialvaporization, adjusting or controlling the flow of cooling fluid, andadjusting or controlling the vacuum system. Adjustment can be inresponse to data obtained by a feedback system. Some examples anddetails of these steps and processes are described above. Furtherexamples and details of each of these steps and processes are describedbelow.

Material Feeding Process

A method for generating nano-scale particles can comprise a materialfeeding process. The material feeding process can include introducing araw material into a vaporization system. The raw material can be insolid or liquid form and may comprise ingots, pellets, powder, rods,wire, coils, bars, etc. The material feeding process can compriseadvancing the raw material into close proximity with a vaporizationsystem 610 at a controllable rate. Advantageously, the material feedingprocess can comprise allowing the raw material to flow into a thin layerover a stationary surface of the vaporization system 610 (wetting)before the raw material changes phase into a vapor.

The method can also comprise adjusting the feeding rate of the rawmaterial so as to maintain a desired vaporization rate or a desiredthickness of a thin layer of raw material on the heater device 610′. Thedesired feeding rate can be determined by observing flow of thevaporized raw material and cooling fluid. Advantageously, the method cancomprise allowing liquid raw material to flow evenly over the stationarysurface of the heater device 610′. Alternatively, the raw material maybe allowed to flow over a convex surface of the heater device 610′. Theraw material may be allowed to flow over a downwardly facing surface ofthe heater device 610′. The feed rate of the raw material may be limitedsuch that only a thin film of raw material forms on the surface of theheater device 610′. The feed rate may be adjusted to limit the thicknessof the film so as to minimize the formation of bubbles during thevaporization of the raw material. Optionally, the adjustments can bemade by a person who observes the layer of raw material or the flow ofraw material onto the heater device 610′. Alternatively, the adjustmentscan be made automatically by a system that responds to the feeding ratewithout need for human input. The adjustments can be accomplishedthrough use of a single or multiple controllers 410′. Optionally, themethod can comprise adjusting the feed rate of raw material to reduce orincrease flow rate and/or turbulence of the flow of material vaporemanating from the heater device 610′.

With reference to FIGS. 2 and 4, in one exemplary embodiment, thematerial feeder 710′ can be activated, including supplying electricalpower, such that the material 910 in the form of metal wire is fed fromthe spool 720 into the outside end 734 of the access tube 730 and movestoward the inner end 732 of the material feeder 710′. The material 910eventually protrudes into the area 116 of the first chamber 112′ justabove the heating element 612. As the material 910 is fed through theaccess tube 730, it is heated by the heating element 612 until shortlyafter protruding from the end 910 of the access tube 730, the material910 softens, bends downwardly toward the heating element 612, and meltsinto liquid form, dripping down onto the heating element 612. Thematerial, upon contacting the heating element 612, quickly forms a thinand continuous layer 920, spreading out over the entire surface of theheating element 612, including the downwardly facing surfaces, and formsa thin, even, liquid layer 920 of material.

With reference to FIGS. 4 and 5, the thin layer 920 of liquefiedmaterial is illustrated as generally adhering to the heating element 612in such a way that it flows freely along, across, and around the surfaceof the heating element 612 but without excessive dripping from theheating element 612.

The material 910 can be fed through the access tube 730 at a faster orslower rate, according to the desires of the operator or the parametersof the automated controller. If it is desired to make the layer 920 onthe heating element 612 thicker, a higher throughput can be achieved byadjusting the controller 410′ appropriately. Pooling of the material onthe heating element 612 can be minimized by decreasing throughput ofmaterial 910 through the material feeder 710, and the process can beobserved using the camera 162. Visually observing a portion of the zone940 allows feedback and adjustment to be made to achieve desiredconditions for nano-particle formation in the vicinity of the heatingelement 612.

Material Vaporization Process

A method for generating nano-scale particles can comprise a vaporizationprocess. The vaporization process can include heating material until itvaporizes. Optionally, the vaporization process can include the materialfeeding process. For example, but without limitation, the vaporizationprocess can comprise contacting a stationary surface of a heater device610′ with a raw material. An advantage is provided where thevaporization process includes vaporizing the material with a heaterdevice 610′ that does not induce a violently turbulent flow. Forexample, but without limitation, the heater device 610′ may allow vaporto flow upwardly, in a laminar manner, from the heater device 610′ underfree convection. Optionally, the heater device 610′ may allow vapor toemanate or flow away from the device under substantially freeconvection. Alternatively, the heater device 610′ may allow vapor toflow in a substantially laminar manner. Optionally, the vaporizationprocess may occur within a closed or partially enclosed chamber.Advantageously, the vaporization process occurs in conjunction with amaterial feeder process like that described above, which can supply rawor yet-to-be vaporized material to the vaporization device at anadjustable rate. Advantageously, the material feeding process cancomprise allowing the raw material to flow into a thin layer over thestationary surface of a heater device 610′ before the raw materialchanges phase into a vapor. Optionally, the vaporization process can beaccomplished by a plurality of heater devices. The heater devices may bedisposed in a chamber, spaced from and adjacent to each other.Alternatively, the material vapor can be created by a number of methodsincluding resistance heating, hollow tube furnace heating or slotfurnace heating.

The vaporization process can comprise the events described below. Thegas molecules of the material separate from the thin liquid layer ofmaterial still present on the surface of the heating element 612 andemanate or move outwardly from the heating element 612 into the spacesurrounding the heating element 612 inside the upper area 116 of thefirst chamber 112′. This separation of gas phase molecules can becompared to boiling. The vaporized material molecules, in accordancewith the principles of physics which govern fluid movement andconvection currents, gently rise upwardly through the area 116 of thefirst chamber 112′ toward the tube 150 at the top of the first chamber112′. The particles in their vaporized, gaseous state have high energy,and they are better able to overcome the constant downward pull ofgravity than are the surrounding, cooler molecules in the chamber. Thus,the vaporized material molecules undergo substantially free convectionas they move upwardly through the first chamber 112′. This generalconvective movement of vaporized molecules is illustrated in FIG. 4 withthe arrows 916. The general region occupied by the material vapor isillustrated in FIG. 4 as general region 930.

With reference to an exemplary but non-limiting embodiment illustratedin FIG. 4, an end-view of the heating element 612 is shown including astylized illustration of the thin liquid layer 920 of material. Asdescribed above, the material layer 920 is heated by the heating element612 to the point at which it changes phase from a liquid to a vapor, orgaseous phase. This phase change occurs inside a general zone 930 nearthe heating element 612, illustrated in FIGS. 4 and 5. Within the zone930, the material in its vaporized form undergoes nucleation and growth,as the vaporized molecules encounter each other and interact to formnano-scale particles. As the nanoparticles continue to float generallyaway from the heating element 612 through the zone 930 undergoingnucleation and growth, they enter into a zone 940, where they are morelikely to interact with molecules of cooling gas.

Within the zone 940, the nano-sized clusters or groups of materialmolecules undergo a change of phase from gas to solid. This phase changemay be from gas phase directly to solid phase in a process calledreverse sublimation, or it may be through phase condensation. The statechange results in nano-sized particles of material that in their newsolid phase are less likely to adhere to other material particles; thus,the particles are able to retain their distinctive nano-scale size. Itis the interaction between cooling gas and vaporized gaseous nano-sizedmaterial molecule groups that results in solid phase nano-scale materialparticles. The cooling fluid process and the interaction betweenquenchant gas and vaporized particles is described in more detail below.

FIG. 7 is a close-up photograph view of the top of the heating element612 inside the particle generator 10′. The heating element 612 extendslaterally through the picture, and the yet-to-be melted or vaporizedmaterial is seen as a protruding wire at the right side of the picture.The functioning heating element 612 radiates both heat and light. Inthis photograph, the heating element 612 is coated with liquid material(zinc) that is undergoing vaporization.

Cooling Process

A method for generating nano-scale particles can also comprise a coolingprocess. The cooling process can include injecting a flow of coolingfluid upwardly from a position below the vaporization device or heaterelement. An advantage is provided where the flow of cooling fluid isgenerally parallel to and in contact with the upward flow of thevaporized raw material. Advantageously, the flow of cooling fluid can beat the same or substantially the same velocity as the flow of vaporizedraw material. Advantageously, the flow of cooling fluid can be inthermal communication with the flow of vaporized raw material.Preferably, the cooling fluid is introduced in such a way as to avoidcreating a highly turbulent flow. For example, but without limitation,the flow of cooling fluid can be injected so as to create a laminar orsubstantially laminar flow. The cooling fluid can be any cooling orquenchant fluid, including any pure gas or mixture of inert or reactivegases (such as, for example, but without limitation, one or anycombination of Helium, Hydrogen, Nitrogen, Argon, Carbon Dioxide,Oxygen, and the like). Materials that can be vaporized at elevatedtemperatures and/or reduced pressures can also be used as cooling gases.Those of skill in the art will recognize the wide variety of fluids andfluid mixtures that can be used as quenchant fluids. Optionally, thecooling gas may be injected into a closed chamber, providing theadvantage of reducing the chances of ignition or explosion if volatilequenchant fluids are employed. The method can comprise passing thecooling fluid through a diffuser. Optionally, the diffuser comprises oneor multiple blocks of sintered stainless steel. Advantageously, thecooling fluid can be introduced into a chamber from a diffuser locatedbelow the vaporization device.

Exemplary but non-limiting embodiments of a system for introducingcooling fluid into proximity with vaporized material are illustrated byFIGS. 2, 2B, 3, and 4. With reference to FIGS. 2, 2B, 3, and 4, thestable quenchant gas can be created by a number of methods, such asintroduction of gas into the first chamber through one or multiplediffusers 118, 119. Advantageously, such diffusers can be placed nearthe bottom of the first chamber 112′. For example, in one exemplary butnon-limiting embodiment illustrated in FIG. 4, the diffuser 118 throughwhich the cooling gas flows is disposed below the heating element 612.The cooling gas flows upwardly as indicated by the arrows 914.Preferably, the shape and size of the diffuser 118 or diffusers as wellas their distance from the source of metal vapor can be configured togenerate a smooth flow of quenchant gas. A violently turbulent and/orchaotic plume can lead to broad particle size distributions.Advantageously, the diffusers can be porous sintered metal diffusers.

The method can also comprise adjusting the flow of cooling fluid so asto maintain a laminar or substantially laminar flow of the vaporized rawmaterial and cooling fluid. Optionally, the adjustments can be made by aperson who observes the interaction between the vapor and cooling fluid.Alternatively, the adjustments can be made automatically by a systemthat responds to the flow characteristics without need for human input.The adjustments can be accomplished through use of a single or multiplecontrollers as described above. Optionally, the method can compriseadjusting the flow of cooling fluid to reduce or increase flow rateand/or turbulence of the cooling fluid. Optionally, the method cancomprise adjusting the flow of cooling fluid such that the flow ofvaporized raw material rising from the heater device 610′ flowsgenerally in the shape of a flame of a candle.

Advantageously, the cooling or quenchant gas is introduced into thediffuser 118 by means of mass flow controllers to precisely meter theflow rate. The size of the nano-particles produced is determined by,among other things, the heat capacity of the quenchant gas, the chamberpressure, the rate of generation of the material vapor and the flow rateof the quenchant gas. Blending a mixture of Helium, Hydrogen, Nitrogenand/or Argon gases by use of multiple mass flow controllers or a mixingdevice configured to receive multiple gas flows and mix them together,can control the heat capacity of the quenchant gas. The mixing devicecan also be configured to control the mass flow of gases into andthrough the particle generator.

In one exemplary, but non-limiting embodiment, the gas flows from one ora plurality of pressurized gas tanks 520, is released from within thetank(s) through the valves 526 (upon opening of the valves 526 using theknobs 528), and flows outwardly from the pressurized tanks 520 throughthe tubes 530 into the mixer 540. The two tanks 520 contain twodifferent kinds of gas that are blended and mixed together inside themixer 540 to achieve desired cooling characteristics. The combinedcooling gas is then allowed to pass through the pipe 550 into the lowerregion 114 of the first chamber 112′ and through the diffuser 118, whichis formed in one embodiment from porous sintered stainless steel. Inthis exemplary embodiment, the volumetric flow rate of the cooling gascan be about 1-5 liters per minute.

This lower region 114, as noted above, can also be embodied asillustrated by the plenum 114B in FIG. 2B. The gas is then allowed totravel through the diffuser 118, flowing generally upwardly from thelower region 114 to the upper region 116 of the first chamber 112′. Thediffuser 118 causes the flow of cooling gas to be spread out evenly fromthe surface of the diffuser 118, such that the gas flow does not createviolently turbulent currents or eddies and flows in a substantiallylaminar manner throughout the lower region 114 of the first chamber112′.

The chamber pressure can be controlled by the vacuum pumps and is alsoaffected by the mass flow of gases in the particle generator 10′. Themass flux of the metal vapor is controlled by the size, geometry andtemperature of the heat source and depends on the metal beingevaporated. The mass flow controller or controllers can precisely meterthe flow rate of the quenchant gas.

As discussed above, and with reference to FIGS. 4 and 5, vaporizedmaterial emanates from the heater device 610′ to occupy a general zone930. The vaporized material undergoes convective movement as illustratedby the arrows 916. This vaporization and convective movement areconcurrent with the flow of cooling gas described above. For example,while the material layer 920 is being vaporized by the heating element612, and replacement material 910 continuously fed onto the heatingelement 612 by the material feeder 710, the operator optionally adjuststhe controller 410′ to begin or continue the flow of cooling gas fromthe cooling fluid delivery system 510′.

Particle Formation

The cooling gas and the material vapor described above interact, andthis interaction between cooling gas and vaporized gaseous nano-sizedmaterial molecule groups results in solid phase nano-scale materialparticles.

FIG. 4 includes an illustration of the spatial zone 940 where thisinteraction occurs. The flow of gas is illustrated in FIG. 3, whichshows a cutaway view of the inside of the first chamber 112′. Theheating element 612 is viewed end-on in FIG. 3 and the flow of gas isindicated by arrows. The gas flow, in this embodiment, is smooth andsubstantially laminar as the gas flows around and past the heatingelement 612 and upwardly toward the tube 150.

FIGS. 4 and 5 show the zones of interaction between the vaporizedparticles of material and the cooling gas in more detail. FIG. 4 shows aclose-up, with more detail, of the heating element 612 inside the firstchamber 112′ shown in FIG. 3. In FIG. 4, the access tube 730 is shownfeeding material 910 to the heating element 612.

FIG. 5 shows a top view of the same zones illustrated in FIG. 4. Theschematic top view of FIG. 5 is similar to what would be seen by thecamera 162 through the window 160 looking downwardly toward the heatingelement 612. FIGS. 4 and 5 indicate a general zone 950 where the coolinggas is flowing smoothly and generally in a laminar manner upwardlythrough the first chamber 112′. Arrows 916 in FIG. 4 illustrate thegeneral upward flow of a stream of solid-phase, condensednano-particles, moving upwardly through free convection combined withthe subtle smooth movement of the flowing cooling gas.

As this cooling interaction occurs, the zone 940 is visible to thecamera 162 looking through the window 160 of the first chamber 112′ dueto increased particle size and light from the heating element. It is thezone 940 that is visible as a plume within the first chamber 112′, asshown in FIGS. 7 through 10 and illustrated in FIG. 4. The thin materiallayer 920 and the zones 930 and 940 are not drawn to scale, because theyare so variable and often thin that such an illustration would bedifficult. FIGS. 7-10 show the visual appearance of the heating element612 glowing with a glowing ring therearound. The glowing ringcorresponds to the zone 940. As shown in FIG. 4, the general zone 940 isvisible, and is in the general shape of a candle flame.

FIGS. 7 through 10 illustrate exemplary but non-limiting examples ofsubstantially laminar flows of zinc vapor being quenched with a mixtureof hydrogen and helium as viewed through a window positioned above theheater device 610′, looking downwardly at the heater device 610′. Inaddition to spreading out the flow of gas spatially, the diffuser 118causes the gas to flow at a steady rate in time, with the rate subjectto adjustment by the operator using the controller 410′. As the coolinggas flows upwardly through the diffuser 118 and into the upper region116 of the first chamber 112′, it flows around and past the heatingelement 612 and thermally communicates with the vaporized molecules ofmaterial.

Discernible in FIG. 7 are the zones of interaction, illustrated in FIGS.4 and 5, between the vaporized particles of material and the coolinggas. The photograph shows the plume, or zone 940 generally toward theright of the photograph and enveloping the heating element. The plume isseen from the top and side. Above the heating element 612 in thephotograph, the zone 940 is seen to be brighter than the blackbackground. Directly in front of the heating element 612, however, theplume or zone 940 is seen to be generally darker against the backdrop ofthe glowing heating element. FIG. 7 also illustrates how thin the zone940 can be in relation to the inner zone 930 and outer zone 950. Becausethe zone 940 is determined by the interaction between material vapor andcooling or quenchant gas, the visible plume can reveal information aboutthe flow pattern of the cooling gas. In this photograph, the plumeincludes some minimal turbulence labeled “t” comprising waves, orundulating perturbations in the flow of cooling gas that helps definethe zone 940. The flow of cooling gas as exhibited by FIG. 7, includingthe turbulence “t,” is intended to be encompassed by the term“substantially laminar.”

FIG. 8 shows a similar view to FIG. 7 and was taken at a different time.The flow of cooling gas as exhibited by FIG. 8 is also intended to beencompassed by the term “substantially laminar.”

FIG. 9 shows a similar view to FIGS. 7 and 8, but shows the plume, orzone 940, as seen from directly above, rather than from above and to theside as in FIGS. 7 and 8. In FIG. 9, the flow of cooling gas is comingtoward the camera and the candle-flame shape is less discernible. Thezone 940 is seen at the perimeter of the photograph as a brighter,rounded, reddish color against the black background. The flow of coolinggas as exhibited by FIG. 9, including the turbulence “t,” is alsointended to be encompassed by the term “substantially laminar.”

FIG. 10 is a photograph of the same heating element as seen in FIGS. 7,8, and 9, showing the plume, or general zone 940, as seen from fartheraway than in FIG. 9, but also from above. The zones 930, 940, and 950 asillustrated in FIG. 5 are all seen in FIG. 10. The internal part of thematerial feeder 710′ is also visible at the right of FIG. 10. The flowof cooling gas as exhibited by FIG. 10 is also intended to beencompassed by the term “substantially laminar.”

Vacuum Storing, and Collecting Processes

A method for generating nano-scale particles can also comprise drawingthe mixed flow of cooling fluid and nano-scale particles with a vacuuminto a collection chamber. Optionally, the cooling gas and vaporized rawmaterial may be drawn from a chamber under a low magnitude vacuum. Themethod can also comprise adjusting the vacuum system so as to maintain alaminar or substantially laminar flow of the vaporized raw material andcooling fluid. Optionally, the adjustments can be made by a person whoobserves the interaction between the vapor and cooling fluid.Alternatively, the adjustments can be made automatically by a systemthat responds to the flow characteristics without need for human input.The adjustments can be accomplished through use of a single or multiplecontrollers as described above. Optionally, the method can compriseadjusting the vacuum to reduce or increase flow rate and/or turbulenceof the cooling fluid. Optionally, the method can comprise adjusting thevacuum system such that the flow of vaporized raw material and coolingfluid flows generally in the shape of a flame of a candle.

In one embodiment, the vacuum system 310′ runs concurrently with all theother systems described above. As noted above, the vacuum system 310′can help create a mild flow of gas from the cooling fluid deliverysystem 510′ through the first chamber 112′ and second chamber 212′,pulling the gas through the filter 222 and ultimately through the tube330 into the vacuum system 310′. The vacuum system 310′ lowers thepressure inside the first and second chambers 112′ and 212′. In oneexemplary but non-limiting embodiment, the vacuum system 310′ lowers thepressure to approximately 1 to 10 Torr below the atmospheric pressure atthe location of the particle generator, or approximately 760 Torr at sealevel. Thus, the vacuum system 310′ gently draws the cooling gasupwardly through the first chamber 112′ and tube 150 into the secondchamber 212′. In an exemplary but non-limiting embodiment, the flow rateof gas through the vacuum system 310′ is about 6 to 10 liters perminute.

FIG. 6 shows a cross-sectional, end-on view of the second chamber 212′where the cross section also cuts through the tube 150. The tube 150 isshown as it enters the second chamber 212′ at an opening 156, located atthe end 154 of the tube 150. Arrows 982 indicate the direction of flowof the nano-scale particles 960 of solid material as well as themolecules 964 of cooling gas shown as stars in FIG. 6.

The gas molecules 964 and nano-particles 960 flow upwardly from thefirst chamber 112′ through the tube 150 at approximately the same rate,and the gas molecules 964 and nano-particles 960 are entrained togetherin the flow. Arrows 984 illustrate how the rate of flow changes as thegas molecules 964 and nano-particles 960 go from the smallercross-sectional volume tube 150 to the larger cross-sectional volumesecond chamber 212′.

As the rate of flow changes, the gas molecules 964 and thenano-particles 960 separate and the smaller gas molecules floatgenerally upwardly from the opening 156 of the tube 150 into the upperregion 230 of the second chamber 212′. In contrast, the nano-particles960, upon exiting the tube 150 through the opening 156 of the secondchamber 212′, fall generally downwardly as indicated by arrows 988 intothe collection region 240 of the second chamber 212′. The arrows 986indicate the general upward movement 986 of the gas molecules relativeto the general downward movement 988 of the solid materialnano-particles 960. The gas molecules 964 do not remain permanentlysuspended in the upper region 230 of the second chamber 212′, but movegenerally toward and through the filter 222, illustrated in FIG. 2,before moving into the frustroconical region 220 of the second chamber212′ and on into the tube 330 and the vacuum system 310′. The generalflow of gas into the vacuum system 310′ does not also move the solidmaterial nano-particles 960 once the particles 960 have entered thesecond chamber 212′ because the filter 222 is configured to allow gasmolecules through while not allowing nano-particles through. From thenano-particle collection region 240 of the second chamber 212′, thenano-particles can be gathered either concurrently while the system isstill operating or after the nano-particle formation system has beenturned off.

Operation and Adjustment

The method can also comprise adjusting or setting the temperature of thevaporization system or heater device 610′ so as to maintain a desiredvaporization rate or a desired thickness of a thin layer of raw materialon the heater device 610′. The desired temperature can be determined byobserving the flow of the vaporized raw material. Optionally, theadjustments can be made by a person who observes the layer of rawmaterial or the flow of raw material into the vaporization system.Alternatively, the adjustments can be made automatically by a systemthat responds to the temperature without need for human input. Theadjustments can be accomplished through use of a single or multiplecontrollers as described above. Optionally, the method can compriseadjusting the temperature of the heater device 610′ to reduce orincrease the temperature and/or rate of emanation of material vaporemanating from the vaporization device. Optionally, the method cancomprise adjusting the flow of cooling fluid such that the flow ofvaporized raw material rising from the heater device 610′ flowsgenerally in the shape of a flame of a candle. The method can comprisesetting the temperature of the heater device 610′ such that the liquidraw material undergoes phase change and is emitted as a vapor generallyuniformly from a surface of the heater device 610′.

In an exemplary but non-limiting embodiment, with continued reference tothe embodiment illustrated by FIG. 2, one method of using the systemsand apparatus described is to first turn on electrical power to theheating element 612 so that the heating element 612 attains atemperature of about 500 degrees Celsius, and begins to give off visiblelight. Optionally, the camera 162 can be used to capture the appearanceof the heater device 610′ and/or record the operation thereof.Concurrently, the cooling system 810 can be activated.

Using a described embodiment, viewing the particle formation processthrough the window 160 of the first chamber 112′ allows the operator toadjust the various controllable systems and observe the effect of thoseadjustments on the size and shape of the zone 940. For example, butwithout limitation, the gas flow from the cooling fluid delivery system510′ can be adjusted to increase or decrease the flow rate so that theflow of gas matches and is entrained with the upward convection of thevaporized material particles. Also affecting the flow rate of coolinggas is the vacuum system 310′ which preferably generates a gentlepressure differential, urging the cooling gas and nano-sized particlesto move upwardly through the tube 150 into the second chamber 212′.

The shape of the zone 940 that is glowing and emitting light to thecamera 162 can indicate to the operator what kind of particle size anduniformity is being created inside the first chamber 112′. Anothercontrollable system that can be adjusted by the operator is the materialfeeder 710.

Concurrent with the operation of the material feeder 710, cooling fluiddelivery system 510′, the activation of the heating element 612, and theoperation of the camera feedback system 162, the vacuum system 310′ andthe cooling system 810 are, in one embodiment, in constant operation.The operator optionally activates these systems either a short timebefore or a short time after activating the other systems alreadydescribed. The cooling system 810 continuously pumps water from thewater tank 820 through the valve 822 and the tube 830 into the coolingjackets 850 and 852 that are attached to the outer surface of the walls122 and 124 of the first chamber 112′. The flow of water through thetube 830 is multi-directional as the pump 840 moves cooled water intothe cooling jackets and pumps warmer water out of the cooling jacketsthrough the tube 830. The water, once pumped into the cooling jackets850 and 852, circulates freely throughout the cooling jackets 850 and852, constantly transferring thermal energy away from the first chamber112′. The valve 822 can be used to regulate the flow of cooling liquidinto and out of the cooling jacket 850 and 852. The valve 822 and thepump 840 can both be controlled and regulated by the controller 410′.

Of course, the foregoing description is that of a preferred particlegenerator and method for generating particles having certain features,aspects, and advantages in accordance with the present inventions.Various changes and modifications also may be made to theabove-described particle generator and method without departing from thespirit and scope of the inventions.

1. A nano-scale particle generator comprising: a first heating devicedisposed in the chamber and configured to vaporize a raw material; and acooling gas source configured to direct a flow of cooling gas intothermal communication with a flow of raw material vapor emanating fromthe first heating device under substantially free convection.
 2. Thegenerator according to claim 1 further comprising a chamber, the firstheating device being disposed in the chamber.
 3. The generator accordingto claim 1, wherein the cooling gas source is further configured todirect the flow of cooling gas at a speed about the same as a speed ofthe flow of raw material vapor
 4. The generator according to claim 1additionally comprising a vacuum device connected to an upper portion ofthe chamber and configured to draw cooling gas and nano-scale particlesof the raw material from the chamber.
 5. The generator according toclaim 1, wherein at least one of the first heater device and the coolinggas supply are configured to allow the raw material vapor and coolinggas to rise above the first heater device in a substantially laminarflow.
 6. The generator according to claim 1 additionally comprising adiffuser disposed at a position below the first heater device.
 7. Thegenerator according to claim 6, wherein the diffuser comprises sinteredstainless steel.
 8. The generator according to claim 6, wherein thediffuser is configured to generate an upward flow of cooling gas beingsubstantially uniform around the first heater device.
 9. The generatoraccording to claim 1, wherein the first heater device is configured toallow the raw material to flow, in a liquid state, substantially evenlyover a stationary surface of the first heater device.
 10. The generatoraccording to claim 9, wherein the first heater device is furtherconfigured to transfer sufficient heat through the stationary surfaceinto the liquid raw material to cause the liquid raw material tovaporize.
 11. The generator according to claim 10, wherein thestationary surface is configured to transfer heat into the liquid rawmaterial so as to cause vaporization of the liquid raw material at asubstantially uniform rate over the stationary surface.
 12. Thegenerator according to claim 1, wherein the first heating device isconfigured to prevent disruption of the flow of raw material vaporemanating therefrom.
 13. The generator according to claim 1 additionallycomprising a second heating device disposed in the chamber andconfigured to vaporize additional raw material.
 14. The generatoraccording to claim 13, wherein the second heating device disposed in thechamber is spaced from and adjacent to the first heating device.